Cigarette smoking continues to be the major preventable cause of death in the United States resulting in nearly 400,000 deaths per year due to cancer and heart disease. Despite the potential adverse health effects, the vast majority of cigarette smokers are unable to cease smoking.
The lack of smoking cessation success is thought to be related to the tobacco withdrawal syndrome or tobacco abstinence syndrome that most smokers experience during their attempts to quit. See, Office of Smoking and Health, The Health Consequences of Smoking: Nicotine Addiction. A Report to the Surgeon General, U.S. Govt. Print. Off., Washington D.C., DHHS Pub. No. (CDC) 88-8406 (1988). The most common effects are similar to those in almost all abstinence syndromes, and include decreased heart rate, anxiety, difficulty concentrating, impatience, irritability and restlessness. See, American Psychiatric Assoc., Diagnostic and Statistical Manual, Washington D.C. (3rd ed. 1980) at pages 159-160, 176-178. Most withdrawal effects occur within 24 hours, peak in the first 1-2 weeks and significantly decrease at one month. It is widely believed that the effects of abstinence from tobacco are due to nicotine deprivation, and that abstinence effects from smoking prevent smokers from stopping. See, J. R. Hughes et al., in Research and Advances in Alcohol and Drug Problems, Vol. 10, L. T. Kozlowski et al., eds., Plenum Pub. Corp. (1990) at pages 317-398.
Of the pharmacological approaches to aiding cessation of smoking, nicotine replacement, e.g., via transdermal nicotine patches or nicotine gum is the most widely used. Nicotine gum decreases abstinence discomfort, especially anxiety, decreased memory and irritability. On the other hand, nicotine gum does not reliably decrease weight gain or craving. Also, discontinuing use of nicotine gum leads to some of the same symptoms as the cigarette withdrawal syndrome. Furthermore, nicotine is toxic, and the availability of nicotine gum or patches poses a risk of poisoning to children and pets.
Other studies have demonstrated that alpha-2 agonists, such as clonidine, decrease postcessation anxiety, irritability and difficulty concentrating. Decreased sympathetic activity has been postulated to be the mechanism by which these drugs decrease abstinence effects. Although tobacco abstinence has some effects that could be attributed to sympathetic activity, it lacks the typical signs and symptoms of sympathetic overactivity, such as tachycardia, diaphoresis and hypertension. Thus, the mechanism by which alpha-2 agonists exert their effects is unclear. While a number of other pharmacological treatments, such as use of doxepin, ACTH, and corticotrophins, for abstinence symptoms have been tested, none of the studies reported baseline and postcessation values for abstinence symptoms. See, for example, S. J. Bourne (U.S. Pat. No. 4,621,074).
Therefore, a continuing need exists for pharmacological treatments that will facilitate smoking cessation, e.g., by blocking or relieving tobacco withdrawal syndrome, or reducing the symptoms of nicotine withdrawal.